Microbiologists incubate samples in sterile liquid culture media to detect and perform tests for pathogenic microorganisms. Salmonella, Listeria, Campylobacter and E. coli are some of the typical microorganisms subject to culturing in this manner. Similar kinds of tests are conducted to detect the presence of microorganisms in samples normally expected to be sterile, such as blood, spinal fluid, medical devices, and a wide variety of industrial materials.
Historically, microbiologists prepare sterile liquid culture solutions and buffered diluent solutions (collectively "culture media") in glass or plastic bottles ("rigid containers"). Although rigid containers can be reused, the preparation of culture media in these containers is expensive, labor intensive, and subject to error.
A laboratory that prepares its own culture media typically undertakes a series of steps. First, the container is washed and rinsed to remove any residual substances or chemicals that may inhibit the growth of microorganisms. Then a measured amount of purified water and a powdered culture mix are placed in the container. The water is heated to dissolve the mix in the water and Ph adjustments are made, as necessary. This is followed by sterilizing the container and its contents in an autoclave. The test sample is then introduced into the culture medium after sterilization.
Because the foregoing procedure is labor intensive, many laboratories now prefer to purchase prefilled and presterilized rigid containers, rather than conduct mixing and sterilization themselves. This leaves the laboratory with the task of merely introducing test samples into the containers after they arrive.
Regardless of whether a lab makes and sterilizes its own culture media or purchases prefilled and presterilized containers, rigid containers have been the containers of choice. They can easily withstand the autoclave conditions (121.degree. C., 15 p.s.i., 100% steam) necessary to sterilize liquid culture media.
Glass is particularly advantageous as a container because it allows visual inspection of the culture media before and after a sample is added. Because it is a rigid container, it can be easily moved from place to place. It rests easily on any flat surface and does not require supporting racks or similar strictures.
In the prefilled situation, the impermeability of glass extends the shelf life of the culture media by preventing evaporative loss. While plastic is used in many instances because it weighs less than glass and is relatively resistant to breakage, many types of plastics cannot withstand autoclave conditions. The types of plastics which can withstand autoclave conditions are expensive, have reduced clarity, and tend to distort or break after repeated autoclave exposure.
In general, rigid containers are expensive to make (the cost of a cap for capped containers can be as much as 25% of the total cost of the container), heavy to ship, subject to breakage, and contribute to total waste disposal. The breakage and weight problems associated with rigid containers are particularly disadvantageous when they are prefilled and presterilized at one geographic location and then shipped to another location for use.
A further problem with rigid containers is that they do not allow a user to easily mix a sample into the culture media. When mixing is required, the container must be shaken to adequately distribute the sample in the media. If shaking will not work because of sample type, the contents of the container must be transferred to a blender bag which is then placed in a machine having reciprocating paddles that pulverize and mix the sample with the culture media. After mixing, the sample and media must be returned to the rigid container for incubation.
As will become apparent, the present invention solves the above problems and provides a more convenient, less expensive, and better way to culture samples.